TW201602043A - Alkali-free float sheet glass, and method for producing alkali-free float sheet glass - Google Patents

Abstract

The present invention relates to an alkali-free float sheet glass which has a glass transition point of 730-850 DEG C, in which the temperature (T4) at which the viscosity (η) is 104 poise is 1220-1350 DEG C, which contains, by mass% on an oxide basis, 57-65% of SiO2, 14-23% of Al2O3, 0-5.5% of B2O3, 1-8.5% of MgO, 3-12% of CaO, 0-10% of SrO and 0-5% of BaO, which contains 12-23% of MgO+CaO+SrO+BaO and 0.1-0.35 mass % of F, which contains 0.3-3 ppm by mass of Cu, which contains 0-0.05 mass % of Cl, and in which the ratio of the quantity (f1) of F in a region at a depth of 1 [mu]m from the top surface of the float sheet glass to the quantity (f2) of F in a region at a depth of 13 [mu]m from the top surface of the float sheet glass (f1/f2) is 0.05-0.5. Defects on the top surface of this alkali-free float sheet glass are suppressed.

Description

Method for producing alkali-free floating flat glass and alkali-free floating flat glass

The present invention relates to a method for producing an alkali-free floating flat glass and an alkali-free floating flat glass which do not substantially contain an alkali metal oxide.

As a method of forming flat glass, a floating method has been widely used. In the floating method, the glass melt which is continuously supplied to the tin melt in the floating kiln (hereinafter also referred to as "kiln") flows on the tin melt to form a strip shape (for example, see Patent Document 1). . The environment in the kiln is set to a reducing environment containing hydrogen gas in order to prevent oxidation of the tin melt. Hydrogen prevents oxidation of the tin melt by reacting with oxygen mixed from the outside.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open Publication No. 2010-53032

When the glass melt is formed in the kiln, there is a case where the particles in the reducing environment are agglomerated and fall to the upper surface of the glass melt and adhere thereto, resulting in defects in the top surface of the manufactured floating flat glass. The top surface refers to the surface on the opposite side to the surface (bottom surface) where the glass ribbon contacts the tin melt when the flat glass is formed by the floating method.

As the use of flat glass has expanded from the field of previous building materials to the field of electronic materials, the defects of the top surface of floating flat glass have become more of a problem. For example, in the case of flat glass for various displays, and the top surface of the floating flat glass, defects in visual size are found. In the case where the top surface of the floating flat glass contains defects, it is treated as a defective product.

When a flat glass for various displays, particularly a metal or oxide film formed on the surface, contains an alkali metal oxide, the alkali metal ions diffuse into the film to deteriorate the film properties, so that substantially no alkali metal ions are contained. A flat glass of alkali.

The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing an alkali-free floating flat glass and an alkali-free floating flat glass in which defects of a top surface are suppressed.

In order to solve the above object, according to one aspect of the present invention, there is provided an alkali-free floating flat glass having a glass transition point of 730 to 850 ° C, a viscosity η of 10 ⁴ poises, a temperature T ₄ of 1220 to 1350 ° C, and oxidation. The mass% of the material standard means: SiO ₂ : 57 to 65%, Al ₂ O ₃ : 14 to 23%, B ₂ O ₃ : 0 to 5.5%, MgO: 1 to 8.5%, and CaO: 3 to 12%. , SrO: 0~10%, and BaO: 0~5%, and MgO+CaO+SrO+BaO is 12~23%, containing 0.1~0.35 mass% of F, containing 0.3~3 mass ppm of Cu, containing 0 ~0.05% by mass of Cl, and the ratio f ₁ /f ₂ of the F amount f ₁ at a depth of 1 μm from the top surface of the floating flat glass to the F amount f ₂ at a depth of 13 μm from the top surface of the floating flat glass is 0.05~0.5.

According to another aspect of the present invention, a method for producing an alkali-free floating flat glass is provided, which is characterized in that it is a method for producing an alkali-free floating flat glass, and comprises the following steps: the F content of the glass raw material is 0.15~ The glass raw material is prepared by adding 1.0% by mass, a Cu content of 0.4 to 6 mass ppm, and a Cl content of 0.15 mass% or less, and the glass raw material is placed in a melting furnace to be melted and clarified to obtain molten glass; The flat glass has an amount of the following components and 0.1 to 0.35 mass% of F, 0.3 to 3 mass ppm of Cu, and 0 to 0.05 mass% of Cl, and the glass transition point is 730 to 850 ° C. The viscosity η becomes 10 ⁴ poises, the temperature T ₄ is 1220 to 1350 ° C, SiO ₂ : 57 to 65%, Al ₂ O ₃ : 14 to 23%, B ₂ O ₃ : 0 to 5.5%, and MgO: 1 to 8.5%. CaO: 3~12%, SrO: 0~10%, BaO: 0~5%, MgO+CaO+SrO+BaO: 12~23%.

According to the present invention, an alkali-free floating flat plate in which defects of the top surface are suppressed can be obtained.

Fig. 1 is a view showing the distribution of the amount of F in the depth direction from the top surface of the floating flat glass.

Fig. 2 is a view showing the distribution of the amount of Cu in the depth direction from the top surface of the floating flat glass.

Fig. 3 is a view showing the distribution of the amount of Cl in the depth direction from the top surface of the floating flat glass.

First, the composition range of each component will be described. In addition, in the following, "%" means "% by mass" unless otherwise specified.

When SiO _{2 is} less than 57%, the glass transition point or strain point does not rise sufficiently, and the coefficient of thermal expansion increases, and the density increases. The amount of SiO ₂ is preferably 58% or more, more preferably 59% or more.

On the other hand, when the amount of SiO ₂ exceeds 65%, the meltability is lowered. The amount of SiO ₂ is preferably 64% or less, more preferably 63% or less, still more preferably 62% or less.

Although Al ₂ O ₃ suppresses the phase separation property of the glass, lowers the coefficient of thermal expansion, and increases the glass transition point or strain point, when it is less than 14%, the effect is not exhibited, and other components which increase the swelling are increased. As a result, the thermal expansion becomes large. The amount of Al ₂ O ₃ is preferably 15% or more, more preferably 16% or more, still more preferably 17% or more.

On the other hand, when the amount of Al ₂ O ₃ exceeds 23%, the meltability of the glass is deteriorated. The amount of Al ₂ O ₃ is preferably 22% or less, more preferably 21% or less.

B ₂ O ₃ is not essential, but may be contained in order to improve the melt reactivity of the glass. The amount of B ₂ O ₃ is preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more.

However, if it is too much, the glass transition point or the strain point will become low, and the amount of B ₂ O ₃ will be 5.5% or less. The amount of B ₂ O ₃ is preferably 5% or less, more preferably 4% or less, still more preferably 3% or less.

MgO has a characteristic that the expansion is not increased in the alkaline earth family, and the glass transition point or the strain point is not excessively lowered, and the meltability is also improved. When the amount of MgO is less than 1%, the above effect by the addition of MgO is not sufficiently exhibited. The amount of MgO is preferably 2% or more, more preferably 3% or more, still more preferably 4% or more.

However, if the amount of MgO exceeds 8.5%, there is a possibility that the devitrification temperature rises. The amount of MgO is preferably 8% or less, more preferably 7% or less, still more preferably 6% or less.

The CaO system has a characteristic of not increasing the expansion in the alkaline earth family and not excessively lowering the glass transition point or the strain point after the MgO, and also improves the meltability. When the amount of CaO is less than 3%, the above effect by the addition of CaO is not sufficiently exhibited. The amount of CaO is preferably 4% or more, more preferably 5% or more, still more preferably 6% or more.

However, if the amount of CaO exceeds 12%, the tightness increases or the devitrification temperature becomes high. The amount of CaO is preferably 11% or less, more preferably 10% or less, still more preferably 9% or less.

SrO is not essential, but may be contained in order to improve the meltability without increasing the devitrification temperature of the glass. The amount of SrO is preferably 0.1% or more, more preferably 0.5% or more, still more preferably 1% or more.

However, if the amount is too large, the expansion coefficient increases, so the amount of SrO is set to 10% or less. The amount of SrO is preferably 9% or less, more preferably 8% or less, still more preferably 7% or less.

BaO is not necessarily required, but is similar to SrO, and may be contained in order to improve the meltability without increasing the devitrification temperature of the glass. The amount of BaO is preferably 0.1% or more, more preferably 0.5% or more, still more preferably 1% or more.

However, if it is too much, the expansion and density of the glass will be excessively increased, so the amount of BaO is 5% or less. The amount of BaO is preferably 4.5% or less, more preferably 4% or less, still more preferably 3.5% or less.

Further, in consideration of an environmental load, BaO is preferably substantially not contained.

SnO ₂ is not an essential component, and it is a component which enhances the clarification property at the time of glass manufacture. SnO ₂ generates oxygen (O ₂ ) in the glass melt obtained by melting the glass raw material. In the glass melt, it is reduced from SnO ₂ to SnO at a temperature of 1450 ° C or higher to generate oxygen, and has a function of causing the bubbles to grow largely. In order to more effectively increase the bubbles, it is preferably melted at 1500 ° C or higher. Glass raw materials. The Sn content in the glass is preferably in terms of SnO ₂ (i.e. SnO ₂ content) of 0.01% or more. When the SnO _{2 is} less than 0.01%, the clearing effect at the time of glass melting cannot be obtained. The SnO ₂ content is preferably 0.02% or more, more preferably 0.05% or more, still more preferably 0.1% or more.

When the content of SnO ₂ exceeds 1%, the color of the glass or the devitrification of the glass may occur. Therefore, the Sn content in the glass is preferably 1% or less in terms of SnO ₂ . The content of SnO _{2 is} more preferably 0.8% or less, further preferably 0.6% or less, further preferably 0.4% or less, and particularly preferably 0.3% or less.

If MgO, CaO, SrO, and BaO are less than 12% in terms of total amount (MgO + CaO + SrO + BaO), the meltability is lacking. The total amount of these is preferably 13% or more, more preferably 14% or more, further preferably 14.5% or more, and particularly preferably 15% or more.

On the other hand, if the total amount of these is more than 23%, there is a possibility that the thermal expansion coefficient cannot be reduced. The total amount of these is preferably 22% or less, more preferably 21% or less, still more preferably 20% or less.

F is contained in order to prevent defects of the top surface of the manufactured floating flat glass.

The mechanism by which the inventors of the present invention have caused defects in the top surface of the manufactured floating flat glass is estimated as follows.

In the kiln, one part of Sn is volatilized from the surface of the tin melt. Further, when the glass composition contains SnO ₂ , a part of Sn is also volatilized from the surface of the glass ribbon in the state of the glass melt.

The glass of the present invention contains Cu in the form of unavoidable impurities. Therefore, in the kiln, one part of Cu is volatilized from the surface of the glass melt.

The volatilized Cu forms an intermetallic compound with Sn, and the intermetallic compound becomes a core, and Sn in the environment in the kiln agglomerates. The agglomerated Sn falls to the upper surface of the glass melt and adheres to become a defect of the top surface of the manufactured floating flat glass.

In the present invention, it is effective especially for suppressing the defects of the top surface of the case where the glass composition contains SnO ₂ .

The inventors of the present invention estimated the mechanism in which the intermetallic compound became a core and the Sn in the environment in the kiln agglomerated.

If Cu forms an intermetallic compound with Sn, the vapor pressure of the environment in which the intermetallic compound exists is lowered. In order to fill the decrease in vapor pressure, the Sn vapor existing around it will approach, thus causing the integration of Sn to be long.

In contrast, in the present invention, in the kiln, a portion of F is volatilized from the surface of the glass melt in the form of F ₂ . The volatilized F ₂ reacts with Sn in the environment to generate SnF ₂ . Since SnF _{2 is} stably present in the environment, Cu and Sn are inhibited from forming an intermetallic compound. Thereby, aggregation of Sn using the intermetallic compound of Cu and Sn as a core is prevented. As a result, it is possible to prevent the agglomerated Sn from falling onto the upper surface of the glass melt and adhering thereto, and it is a defect of the top surface of the manufactured floating flat glass.

When the F content is 0.1% or less, the above effect by the addition of F is not sufficiently exhibited. The F content is preferably 0.13% or more, more preferably 0.15% or more, and still more preferably 0.17%. on.

However, if the F content exceeds 0.35%, the glass transition point or strain point is liable to lower. The F content is preferably 0.3% or less, more preferably 0.25% or less, still more preferably 0.23% or less.

However, if the Cl content of the glass is high, the effect of the above-mentioned addition by F may be hindered, resulting in defects in the top surface of the produced floating flat glass.

The inventors of the present invention estimated the reason why the effect of the above-mentioned F addition is hindered if the Cl content of the glass is high.

In the kiln, a portion of Cl is volatilized from the surface of the glass melt in the form of Cl ₂ . The volatilized Cl ₂ reacts with Sn in the environment to form SnCl ₂ . Since Cl is more reactive with Sn than F, it preferentially causes the reaction of Sn with Cl, and the reaction between Sn and F is hindered.

The temperature in the environment of the kiln is 700~1250 °C, especially the temperature on the upstream side is 900~1250 °C. In this temperature region, the stability of SnCl ₂ is lower than that of SnF ₂ , so there is a tendency to dissociate into Sn and Cl ₂ . Further, the dissociated Sn forms an intermetallic compound with Cu, and the intermetallic compound becomes a core, and Sn in the environment in the kiln agglomerates.

If the Cl content exceeds 0.05%, the effect by the addition of F is hindered by the above effects. Therefore, the Cl content is 0.05% or less. The Cl content is preferably 0.02% or less, more preferably 0.015% or less, still more preferably 0.013% or less.

There is also a case where Cl is contained in the glass of the present invention in order to improve the clarity at the time of glass production. In this case, the Cl content is preferably 0.003% or more, more preferably 0.005% or more, still more preferably 0.007% or more.

As described above, the glass of the present invention contains Cu in the form of unavoidable impurities. The Cu content is 0.3 to 3 mass ppm, preferably 0.4 to 2 mass ppm, more preferably 0.4 to 1.5 mass ppm, still more preferably 0.5 to 1.3 mass ppm.

As described above, in the manufacturing process of the floating flat glass of the present invention, a portion of the F in the kiln is volatilized from the surface of the glass melt, so that the amount of F near the top surface of the manufactured floating flat glass is lower than that of the float. The amount of F inside the flat glass. Specifically, the F amount of the floating flat glass from the top surface depth of 1 μm is f ₁ , and the F amount of the floating flat glass from the top surface depth of 13 μm is f ₂ , at this time, f The ratio of ₁ to f ₂ f ₁ /f ₂ is 0.05 to 0.5.

In the present specification, f ₁ is an average value of the amount of F of the region of the floating flat glass from the top surface depth of 0.9 to 1.1 μm. f ₂ is the average value of the amount of F of the area of the floating flat glass from the top surface depth of 12.9 to 13.1 μm, and is substantially equal to the amount of F inside the floating flat glass.

f ₁ and f ₂ can be obtained by obtaining a depth direction distribution of the F amount from the top surface of the glass by a secondary ion mass spectrometry (SIMS) method. The SIMS analysis conditions are as follows.

Device: IMS-7f manufactured by AMETEK

Primary ion species: Cs ⁺

Acceleration voltage of primary ion: 15kV

Detection area: 30μm

Secondary ion polarity: negative

Monitor secondary ions: ¹⁹ F, ²⁸ Si (or ³⁰ Si)

Neutralization method: by Pt coating and electron beam irradiation on the surface of the sample.

Standard sample for concentration quantification: Ion implantation of ¹⁹ F on a thermal oxide film (SiO ₂ film) on a Si wafer.

f ₁ /f _{2 is} preferably 0.1 to 0.44, more preferably 0.14 to 0.42, still more preferably 0.2 to 0.4, still more preferably 0.25 to 0.38.

As described above, in the manufacturing process of the floating flat glass of the present invention, a part of Cu in the kiln is volatilized from the surface of the glass melt, so that the amount of Cu near the top surface of the manufactured floating flat glass is lower than that of the float. The amount of Cu inside the flat glass. Specifically, the amount of Cu at a depth of 0.5 μm from the top surface of the floating flat glass is cu ₁ , and the amount of Cu at a depth of 8 μm from the top surface of the floating flat glass is cu ₂ . ratio cu cu _{cu. 1} and ₂ of the ₁ / cu ₂ is 0.05 to 0.7.

In the present specification, cu ₁ is an average value of the amount of Cu in the region of the floating flat glass from the top surface depth of 0.4 to 0.6 μm. Cu ₂ is the average value of the amount of Cu in the region of the floating flat glass from the top surface depth of 7.9 to 8.1 μm, and is substantially equal to the amount of Cu inside the floating flat glass.

Cu ₁ and cu _{2 are the} same as f ₁ and f ₂ and can be obtained by obtaining the depth direction distribution of the amount of Cu from the top surface of the glass by the SIMS method. For the measurement of Cu, ⁶³ Cu and ²⁸ Si (or ³⁰ Si) were selected as the secondary ions for monitoring, and ⁶³ Cu was ion-implanted into the thermal oxide film (SiO ₂ film) on the Si wafer as a standard sample for quantification.

Cu ₁ /cu _{2 is} preferably 0.1 to 0.6, more preferably 0.15 to 0.55, still more preferably 0.2 to 0.5, still more preferably 0.25 to 0.45.

As described above, in the manufacturing process of the floating flat glass of the present invention, a part of Cl in the kiln is volatilized from the surface of the glass melt, so that the amount of Cl near the top surface of the manufactured floating flat glass becomes lower than the float. The amount of Cl inside the flat glass. Specifically, the amount of Cl at a depth of 1 μm from the top surface of the floating flat glass is set to cl ₁ , and the amount of Cl at a depth of 13 μm from the top surface of the floating flat glass is set to cl ₂ , at this time, cl The ratio of ₁ to cl ₂ cl _l /cl ₂ is 0.05 to 0.85.

In the present specification, cl ₁ is an average value of the amount of Cl of the floating plate glass in the region from the top surface depth of 0.9 to 1.1 μm. Cl ₂ is the average value of the amount of Cl in the region from the top surface depth of 12.9 to 13.1 μm of the floating flat glass, and is substantially equal to the amount of Cl inside the floating flat glass.

Cl ₁ and cl _{2 are the} same as f ₁ and f ₂ and can be obtained by obtaining the depth direction distribution of the amount of Cl from the top surface of the glass. For the measurement of Cl, ³⁵ Cl and ²⁸ Si (or ³⁰ Si) were selected as the secondary ions for monitoring, and the thermal oxidation film (SiO ₂ film) on the Si wafer was ion-implanted with ³⁵ Cl as a standard sample for quantification.

Cl ₁ /cl _{2 is} preferably 0.1 to 0.8, more preferably 0.2 to 0.75, still more preferably 0.3 to 0.7, still more preferably 0.35 to 0.65.

Since the floating flat glass of the present invention has a glass transition point of 730 to 850 ° C, heat shrinkage at the time of panel manufacture can be suppressed. Further, as a method of producing the p-SiTFT, a solid phase crystallization method can be applied.

Since the floating flat glass of the present invention has a glass transition point of 730 to 850 ° C, it is suitable for high glass transfer points or high strain point applications (for example, a display substrate for an organic EL (electroluminescence) or a substrate for illumination) Or a substrate for a display or a substrate for illumination of a sheet having a thickness of 100 μm or less. However, if the glass transition point is too high, there is a possibility that defects are likely to occur during floating forming of the glass. Therefore, the glass transition point is preferably 740 to 840 ° C, more preferably 750 to 820 ° C, and still more preferably 760 to 800 ° C.

The viscosity η of the floating flat glass of the present invention becomes 10 ⁴ poises and the temperature T ₄ is 1220 to 1350 °C. T ₄ is a standard which is a standard for floating formability, and when T ₄ is 1220 to 1350 ° C, it is preferable to form the glass by a float method.

T _{4 is} preferably 1330 ° C or lower, more preferably 1310 ° C or lower, and still more preferably 1300 ° C or lower.

Next, a method of manufacturing the floating flat glass will be described.

The method for producing a floating flat glass according to the present embodiment includes a melting step, a clarifying step, a forming step, a slow cooling step, and a cutting step, and further includes a polishing step as needed. The grinding step is carried out according to the use of the glass plate.

The melting step is to prepare a plurality of glass raw materials, and the glass raw materials are put into a melting furnace for melting to obtain molten glass. After the glass raw material is put into the melting furnace, it is melted by the radiant heat of the flame sprayed from the burner to become molten glass.

The clarification step is a step of removing bubbles in the molten glass. In order to effectively remove the bubbles, F, Cl, SnO ₂ , SO ₃ , Fe ₂ O ₃ or the like is used as a clarifying agent in the production of the alkali-free floating flat glass. F and Cl are components which generate a large amount of bubbles when the raw material is heated and which increase the number of bubbles, and use them in combination with SO ₃ and Fe ₂ O ₃ to drastically enhance the clarifying effect. These may generally be added in the form of a fluoride or chloride of an alkaline earth.

The forming step is that the molten glass obtained in the clarification step is continuously supplied to the molten tin in the kiln, and the molten glass is flowed on the molten tin to be shaped to obtain a glass ribbon. turn off In order to prevent oxidation of molten tin in the environment in the kiln, it is preferable to contain a mixed gas (reducing gas) of hydrogen and nitrogen. The ratio of hydrogen in the reducing gas is 0.1 to 15% by volume. The temperature in the environment of the kiln is 700~1250 °C, especially the temperature on the upstream side is 900~1250 °C. The glass ribbon is cooled while flowing in a specific direction, and is pulled from the molten tin near the exit of the kiln.

The slow cooling step is to slowly cool the glass ribbon obtained in the forming step in a slow cooling furnace. Since the inlet of the slow cooling furnace faces the outlet, the glass belt is horizontally conveyed on the side of the roller to be slowly cooled. A sulfur dioxide (SO ₂ ) gas or the like is blown onto the surface of the glass ribbon near the inner side of the inlet of the slow cooling furnace to form a protective film on the surface layer of the glass ribbon.

The cutting step is to cut the glass ribbon which has been slowly cooled in the slow cooling step into a specific size by a cutter. In the cutting step, both edge portions (so-called edge materials) in the width direction orthogonal to the traveling direction of the glass ribbon are cut off.

When the F content in the glass is 0.1 to 0.35 mass%, since F is volatilized in the melting step and the clarification step, it is preferred to prepare the glass raw material so that the F content in the glass raw material is 0.15 to 1.0% by mass. The F content in the glass raw material is preferably 0.25 mass% or more, more preferably 0.35 mass% or more. Further, it is preferably 0.8% by mass or less, more preferably 0.6% by mass or less.

When the content of Cu in the glass is 0.3 to 3 ppm by mass, since Cu is volatilized in the melting step and the clarification step, it is preferred to prepare the glass raw material such that the Cu content in the glass raw material is 0.4 to 6 ppm by mass. Since Cu is contained in the glass raw material in the form of unavoidable impurities, the Cu content in the glass raw material is preferably 0.5 ppm by mass or more. Further, it is preferably 4 ppm by mass or less, more preferably 2 ppm by mass or less.

When the Cl content in the glass is from 0 to 0.05% by mass, since the Cl is volatilized in the melting step and the clarification step, it is preferred to prepare the glass raw material such that the Cl content in the glass raw material is 0.15% by mass or less. The content of Cl in the glass raw material is preferably 0.06% by mass or less, more preferably 0.03% by mass or less.

In the present embodiment, in order to set the ratio f ₁ /f ₂ to 0.05 to 0.5, the amount of F diffused from the surface of the glass melt in the kiln is controlled. The following six forming conditions are adjusted to control the amount of F volatilization in the kiln: first, the temperature of the molten glass flowing into the kiln; second, the temperature distribution of the traveling direction of the glass ribbon in the kiln; third, the kiln The temperature distribution in the width direction orthogonal to the traveling direction of the glass ribbon; the fourth, the glass ribbon transport speed on the roller of the slow cooling furnace; the fifth, the input amount and/or the exhaust gas amount of the reducing gas in the kiln; , the hydrogen concentration of the reducing gas. It is necessary not only to adjust individual conditions individually, but also to make careful adjustments in consideration of mutual correlation. In order to set the ratio cu ₁ /cu ₂ to 0.05 to 0.7 and the ratio cl ₁ /cl ₂ to 0.05 to 0.85, the six molding conditions were adjusted to control the amount of Cu volatilization and the amount of Cl volatilization in the kiln.

[Examples]

Hereinafter, the present invention will be described in detail using examples. However, the present invention is not limited to this.

(Reference example)

In the present reference example, in order to simulate the phenomenon in which Sn in the kiln is agglomerated by using an intermetallic compound of Cu and Sn as a core, the following test was carried out.

Test content

In order to simulate the volatilization of Sn in the kiln, a compound [(A) to (C)] which generates a gas containing Sn is placed at the bottom of the container made of Al ₂ O ₃ . The fine particles (Cu) which are the cores during the aggregation of Sn are attached to the quartz substrate which is the lid of the container made of Al ₂ O ₃ . Then, in a N ₂ atmosphere, rapid heating (1100 ° C / 2 minutes) was carried out together with the vessel to produce a gas containing Sn. After the container was cooled, the lower surface of the quartz substrate was observed with an optical microscope, and the number of particles having a size of 5 μm or more in a field of view of 500 × 300 μm was measured. Since the aggregate of Sn falls to the upper surface of the glass melt when it grows to a size of about 10 μm, the risk of defects on the top surface of the floating flat glass can be confirmed by measuring the number of particles having a size of 5 μm or more. .

Condition 1: No compound

Condition 2: Compound (A) (SnCl ₂ )

Condition 3: Compound (B) (SnF ₂ )

Condition 4: Compound (C) (SnCl ₂ , SnF ₂ )

Condition 1 is a simulation of the fact that Sn does not diverge in the kiln. The number of particles having a size of 5 μm or more is zero, and there is less risk of defects occurring on the top surface of the floating flat glass.

Condition 2 is a simulation of the scattering of Sn and Cl ₂ in the kiln. The number of particles having a size of 5 μm or more is 10, and there is a high risk of defects occurring on the top surface of the floating flat glass.

Condition 3 simulates the case where Sn and F ₂ are being volatilized in the kiln. The number of particles having a size of 5 μm or more is zero, and there is less risk of defects occurring on the top surface of the floating flat glass.

Condition 4 simulates the case where Sn, F ₂ and Cl _{2 are} volatilized in the kiln. The number of particles having a size of 5 μm or more is five, and there is a high risk of defects occurring on the top surface of the floating flat glass.

In the present embodiment, the distribution of the F amount, the Cu amount, and the Cl amount in the depth direction from the top surface of the floating flat glass is obtained by the SIMS method. The SIMS analysis conditions are as follows.

Device: IMS-7f manufactured by AMETEK

Primary ion species: Cs ⁺

Acceleration voltage of primary ion: 15kV

Detection area: 30μm

Secondary ion polarity: negative

Monitor secondary ions: ¹⁹ F, ⁶³ Cu, ³⁵ Cl, ²⁸ Si (or ³⁰ Si)

Neutralization method: by Pt coating and electron beam irradiation on the surface of the sample

Standard sample for concentration quantification: Prepare monitoring of secondary ions one by one. Three thermal oxide films (SiO ₂ films) on the Si wafer were ion-implanted with ¹⁹ F, ⁶³ Cu, and ³⁵ Cl, respectively.

The floating flat glass contains 61% by mass of SiO ₂ , 20% by mass of Al ₂ O ₃ , 1% by mass of B ₂ O ₃ , 6% by mass of MgO, 5% by mass of CaO, and 7% by mass of SrO, 0.2. The mass% of SnO ₂ and MgO+CaO+SrO+BaO is 18% by mass, and contains 0.2% by mass of F, contains 0.5 ppm by mass of Cu, and contains 0.01% by mass of Cl.

The floating plate glass has a glass transition point of 760 ° C and a T ₄ of 1300 ° C.

In order to obtain the floating flat glass, the glass raw material is prepared so that the F content in the glass raw material is 0.4% by mass, the Cu content is 0.6 ppm by mass, and the Cl content is 0.02% by mass, and the glass raw material is put into a melting furnace for melting. And clarify to obtain molten glass.

Fig. 1 is a view showing the distribution of the amount of F in the depth direction from the top surface of the floating flat glass. Fig. 2 is a view showing the distribution of the amount of Cu in the depth direction from the top surface of the floating flat glass. Fig. 3 is a view showing the distribution of the amount of Cl in the depth direction from the top surface of the floating flat glass.

It can be confirmed from Fig. 1 that the ratio f ₁ /f ₂ of the F amount f ₁ at a depth of 1 μm from the top surface of the floating flat glass to the F amount f ₂ at a depth of 13 μm from the top surface of the floating flat glass is 0.44. Meet 0.05~0.5.

In order to set the ratio f ₁ /f ₂ to 0.44, the following six molding conditions are adjusted: first, the temperature of the molten glass flowing into the kiln; second, the temperature distribution of the traveling direction of the glass ribbon in the kiln; 3. The temperature distribution in the width direction of the kiln orthogonal to the traveling direction of the glass ribbon; the fourth, the conveying speed of the glass ribbon on the roller of the slow cooling furnace; the fifth, the input amount and/or the row of the reducing gas in the kiln Gas volume; sixth, the hydrogen concentration of the reducing gas. Not only the individual conditions were individually adjusted, but also the mutual correlation was considered and the molding was carefully adjusted to obtain a floating flat glass having a ratio f ₁ /f ₂ of 0.44.

It can be confirmed from Fig. 2 that the ratio cu ₁ /cu ₂ of the Cu amount cu ₁ at a depth of 0.5 μm from the top surface of the floating flat glass to the Cu amount cu ₂ at a depth of 8 μm from the top surface of the floating flat glass is 0.33. , meets 0.05~0.7.

The above six molding conditions were adjusted to form a floating flat glass having a ratio of cu ₁ /cu ₂ of 0.33.

Can be confirmed from FIG. 3: Cl 1μm depth amount from the top surface of flat glass floating Cl _{cl. 1} and the amount of the depth of 13μm from the top surface of the sheet glass float cl cl ₂ ratio of ₁ / cl ₂ 0.47, Meet 0.05~0.85.

The above six molding conditions were adjusted to form, and a floating flat glass having a ratio of cl ₁ /cl ₂ of 0.47 was obtained.

The present invention has been described in detail with reference to the specific embodiments thereof. It is to be understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

In addition, the present application is based on a Japanese patent application filed on May 21, 2014 (Japanese Patent Application No. 2014-105192), the entire contents of which is incorporated herein by reference.

Claims (5)

An alkali-free floating flat glass having a glass transition point of 730 to 850 ° C, a viscosity η of 10 ⁴ poises, a temperature T ₄ of 1220 to 1350 ° C, and expressed by mass % of oxide, containing: SiO ₂ : 57 ~65%, Al ₂ O ₃ : 14 to 23%, B ₂ O ₃ : 0 to 5.5%, MgO: 1 to 8.5%, CaO: 3 to 12%, SrO: 0 to 10%, and BaO: 0~ 5%, and MgO+CaO+SrO+BaO is 12 to 23%, containing 0.1 to 0.35 mass% of F, containing 0.3 to 3 mass ppm of Cu, containing 0 to 0.05 mass% of Cl, and floating flat glass The ratio f ₁ /f ₂ of the F amount f _{1 in} the region having a depth of 1 μm from the top surface to the F amount f ₂ at a depth of 13 μm from the top surface of the floating flat glass is 0.05 to 0.5. The alkali-free floating flat glass of claim 1, which further contains 0.01 to 1% by mass of SnO ₂ . The alkali-free floating flat glass of claim 1 or 2, wherein the floating flat glass has a Cu amount cu ₁ at a depth of 0.5 μm from the top surface and a depth of 8 μm from the top surface of the floating flat glass The ratio cu ₁ /cu ₂ of the Cu amount cu ₂ is 0.05 to 0.7. The alkali-free floating flat glass according to any one of claims 1 to 3, wherein the floating plate glass has a Cl amount cl ₁ at a depth of 1 μm from the top surface and a depth from the top surface of the floating flat glass Cl cl 13μm at an amount cl ₂ ratio of ₁ / cl ₂ is 0.05 to 0.85. The invention relates to a method for producing an alkali-free floating flat glass, which is characterized in that it is a method for producing an alkali-free floating flat glass, and comprises the following steps: the F content of the glass raw material is 0.15-1.0 mass%, and the Cu content is 0.4~ The glass raw material is prepared in a manner of 6 mass ppm and a Cl content of 0.15% by mass or less, and the glass raw material is charged into a melting furnace to be melted and clarified to obtain molten glass; the mass of the alkali-free floating flat glass is based on an oxide % indicates the following components, and 0.1 to 0.35 mass% of F, 0.3 to 3 mass ppm of Cu, and 0 to 0.05 mass% of Cl, and the glass transition point is 730 to 850 ° C, and the viscosity η becomes a temperature T of 10 ⁴ poise. ₄ is 1220~1350 °C, SiO ₂ : 57~65%, Al ₂ O ₃ : 14~23%, B ₂ O ₃ : 0~5.5%, MgO: 1~8.5%, CaO: 3~12%, SrO : 0~10%, BaO: 0~5%, MgO+CaO+SrO+BaO: 12~23%.